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DOE OSTI2018

Search for excited Bc + states

A search is performed in the invariant mass spectrum of the B c + π + π - system for the excited B c + states B c (2 1 S 0 ) + and B c (2 3 S 1 ) + using a data sample of pp collisions collected by the LHCb experiment at the centre-of-mass energy of $\sqrt{s}$=8 TeV, corresponding to an integrated luminosity of 2 fb -1 . No evidence is seen for either state. Upper limits on the ratios of the production cross-sections of the B c (2 1 S 0 ) + and B c (2 3 S 1 ) + states times the branching fractions of Bc(21S0)+ → B c + π + π - and B c (2 3 S 1 ) + → B c * + π + π - over the production cross-section of the Bc+ state are given as a function of their masses. They are found to be between 0.02 and 0.14 at 95% confidence level for Bc(2 1 S 0 ) + and B c (2 3 S 1 ) + in the mass ranges [6830, 6890] MeV/c 2 and [6795, 6890] MeV/c 2 , respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Measurement of the W boson mass

The W boson mass is measured using proton-proton collision data at $\sqrt{s}$ = 13 TeV corresponding to an integrated luminosity of 1.7 fb -1 recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon $q/ρ_T$ distribution of a sample of W →$μv$ decays and the $\phi^*$ distribution of a sample of Z → $μμ$ decays the W boson mass is determined to be $m_w$ =80354±23 stat ±10 exp ±17 theory ±9 PDF MeV, where uncertainties correspond to contributions from statistical, experimental systematic, theoretical and parton distribution function sources. This is an average of results based on three recent global parton distribution function sets. The measurement agrees well with the prediction of the global electroweak fit and with previous measurements.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2022

Study of $\mathrm{B}_{c}^{+}$ decays to charmonia and three light hadrons

Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb -1 collected with the LHCb detector, seven decay modes of the $B^+_c$ meson into a $J/ψ$ or $ψ(2S)$ meson and three charged hadrons, kaons or pions, are studied. The decays $B^+_c$ → $(ψ(2S)$ →J/$ψπ^+π^-$)$π^+$, $B^+_c$→$ψ(2S)π^+π^-π^+, B^+_c$→ J/$ψK^+π^-π^+$ and $B^+_c$ → J/$ψK^+K^-K^+$ are observed for the first time, and evidence for the $B^+_c$ →$ψ(2S)K^+K^-π^+$, decay is found, where J/ψ and $(ψ(2S)$ mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different $B^+_c$ decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Search for the radiative $Ξ_b^{-}$ → $Ξ^-γ$ decay

The first search for the rare radiative decay $Ξ_b^{-}$ → $Ξ^-γ$ is performed using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb -1 . $Ξ_b^{-}$ → $Ξ^-J/ψ$ channel is used as normalization. No $Ξ_b^{-}$ → $Ξ^-γ$ signal is found and an upper limit of $\mathcal{B}$( $Ξ_b^{-}$ → $Ξ^-γ$) < 1.3 x 10 -4 at 95% confidence level is obtained.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2022

A theory of dark pions

We present a complete model of a dark QCD sector with light dark pions, broadly motivated by hidden naturalness arguments. The dark quarks couple to the Standard Model via irrelevant Z- and Higgs-portal operators, which encode the low-energy effects of TeV-scale fermions interacting through Yukawa couplings with the Higgs field. The dark pions, depending on their CP properties, behave as either composite axion-like particles (ALPs) mixing with the Z or scalars mixing with the Higgs. The dark pion lifetimes fall naturally in the most interesting region for present and proposed searches for long-lived particles, at the LHC and beyond. This is demonstrated by studying in detail three benchmark scenarios for the symmetries and structure of the theory. Within a coherent framework, we analyze and compare the GeV-scale signatures of flavor-changing meson decays to dark pions, the weak-scale decays of Z and Higgs bosons to hidden hadrons, and the TeV-scale signals of the ultraviolet theory. New constraints are derived from B decays at CMS and from Z-initiated dark showers at LHCb, focusing on the displaced dimuon signature. We also emphasize the strong potential sensitivity of ATLAS and CMS to dark shower signals with large multiplicities and long lifetimes of the dark pions. As a key part of our phenomenological study, we perform a new data-driven calculation of the decays of a light ALP to exclusive hadronic Standard Model final states. The results are provided in a general form, applicable to any model with arbitrary flavor-diagonal couplings of the ALP to fermions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2022

Measurement of $χ_{c1}$(3872) production in proton-proton collisions at $\sqrt{s}$ = 8 and 13 TeV

The production cross-section of the $χ_{c1}$(3872) state relative to the $ψ(2S)$ meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of $\sqrt{s}$ = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb -1 , respectively. The two mesons are reconstructed in the $J/ψπ^+π^-$ final state. The ratios of the prompt and nonprompt $χ_{c1}$(3872) to $ψ(2S)$ production cross-sections are measured as a function of transverse momentum, $ρ_T$, and rapidity, y, of the $χ_{c1}$(3872) and $ψ(2S)$ states, in the kinematic range 4 < $ρ_T$ < 20 GeV/c and 2.0< y < 4.5. The prompt ratio is found to increase with $ρ_T$, independently of y. For the prompt component, the double ratio of the $χ_{c1}$(3872) and $ψ(2S)$ production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of $ρ_T$ and centre-of-mass energy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2022

Measurement of prompt charged-particle production in pp collisions at $\sqrt{s}$ = 13 TeV

The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV. The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of 5.4 nb -1 . The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges $p_T$ ∋ [80, 10 000) MeV/c and η ∋ [2.0, 4.8) and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2024

Measurement of prompt D + and ${D}_s^{+}$ production in p Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

The production of prompt D + and $D^+_s$ mesons is studied in proton-lead collisions at a centre-of-mass energy of $\sqrt{^{S}NN}$ = 5.02 TeV. The data sample corresponding to an integrated luminosity of (1.58 ± 0.02)nb –1 is collected by the LHCb experiment at the LHC. The differential production cross-sections are measured using D + and $D^+_s$ candidates with transverse momentum in the range of 0 < p T < 14 GeV/c and rapidities in the ranges of 1.5 < y* < 4.0 and –5.0 < y* < –2.5 in the nucleon-nucleon centre-of-mass system. For both particles, the nuclear modification factor and the forward-backward production ratio are determined. These results are compared with theoretical models that include initial-state nuclear effects. In addition, measurements of the cross-section ratios between D + , $D^+_s$ and D 0 mesons are presented, providing a baseline for studying the charm hadronization in lead-lead collisions at LHC energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Angular analysis of the B o → K *o μ + μ – decay using 3 fb –1 of integrated luminosity

An angular analysis of the B o → K *o (→ K + π – )μ + μ – decay is presented. The dataset corresponds to an integrated luminosity of 3.0 fb –1 of pp collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine CP-averaged observables and CP asymmetries, taking account of possible contamination from decays with the K + π – system in an S-wave configuration. The angular observables and their correlations are reported in bins of q 2 , the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for q 2 -dependent decay amplitudes in the region 1.1 < q 2 < 6.0 GeV 2 /c 4 , the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of CP-averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Study of D$^{sJ}_{()+}$ mesons decaying to D + K$_{0}^{S}$ and D *0 K + final states

A search is performed for D$^{sJ}_{(*)+}$ mesons in the reactions pp → D *+ K$_{0}^{S}$X and pp → D *0 K + X using data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb detector. For the D * + K$_{0}^{S}$ final state, the decays D *+ → D 0 π + with D 0 → K - π + and D 0 → K - π + π + π - are used. For D *0 K + , the decay D *0 → D 0 π 0 with D 0 → K - π + is used. A prominent D s1 (2536) + signal is observed in both D* +K$_{0}^{S}$ and D* 0 K + final states. The resonances D $^{s1}_{*}$ (2700) + and D $^{s3}_{*}$ (2860) + are also observed, yielding information on their properties, including spin-parity assignments. The decay D $^{s2}_{*}$ (2573) + → D* + K$_{0}^{S}$ is observed for the first time, at a significance of 6.9 σ, and its branching fraction relative to the D $^{s2}_{*}$ (2573) + → D + K$_{0}^{S}$ decay mode is measured.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

Measurement of branching fractions of charmless four-body Λ o b and Ξ o b decays

A search for charmless four-body decays of Λ o b and Ξ o b baryons with a proton and three charged mesons (either kaons or pions) in the final state is performed. The data sample used was recorded in 2011 and 2012 with the LHCb experiment and corresponds to an integrated luminosity of 3 fb –1 . Six decay modes are observed, among which Λ o b → pK – π + π – , Λ o b → pK – K + K – , Ξ o b → pK – π + π – and Ξ o b → pK – π + K – are established for the first time. Their branching fractions (including the ratio of hadronisation fractions in the case of the Ξ o b baryon) are determined relative to the Λ o b → Λ c + π – decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Measurement of differential $ b\overline{b} $- and $ c\overline{c} $-dijet cross-sections in the forward region of pp collisions at $ \sqrt{s} $ = 13 TeV

The inclusive $ b\overline{b} $ - and $ c\overline{c} $ -dijet production cross-sections in the forward region of pp collisions are measured using a data sample collected with the LHCb detector at a centre-of-mass energy of 13 TeV in 2016. The data sample corresponds to an integrated luminosity of 1.6 fb - 1 . Differential cross-sections are measured as a function of the transverse momentum and of the pseudorapidity of the leading jet, of the rapidity difference between the jets, and of the dijet invariant mass. A fiducial region for the measurement is defined by requiring that the two jets originating from the two b or c quarks are emitted with transverse momentum greater than 20 GeV/ c , pseudorapidity in the range 2 . 2 < η < 4 . 2, and with a difference in the azimuthal angle between the two jets greater than 1.5. The integrated $ b\overline{b} $ -dijet cross-section is measured to be 53 . 0 ± 9 . 7 nb, and the total $ c\overline{c} $ -dijet cross-section is measured to be 73 ± 16 nb. The ratio between $ c\overline{c} $ - and $ b\overline{b} $ -dijet cross-sections is also measured and found to be 1 . 37 ± 0 . 27. The results are in agreement with theoretical predictions at next-to-leading order.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2021

Study of ${\mathrm{B}}_{\mathrm{s}}^0$ → J/ψπ + π – K + K – decays

The decays ${\mathrm{B}}_{\mathrm{s}}^0$ → J/ψπ + π – K + K – are studied using a data set corresponding to an integrated luminosity of 9 fb –1 , collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The decays ${\mathrm{B}}_{\mathrm{s}}^0$ → $\mathrm{J}/{ψ \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0}$ and ${\mathrm{B}}_{\mathrm{s}}^0$ → χ c1 (3872)K + K – , where the K + K – pair does not originate from a Φ meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate χ c1 (3872)Φ, $\mathrm{J}/{ψ \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0}$, ψ(2S)Φ and χ c1 (3872)K + K – states are reported. A structure, denoted as X(4740), is observed in the J/ψΦ mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be ${\displaystyle \begin{array}{c}{m}_{\mathrm{X}(4740)}=4741\pm 6\pm 6\kern0.5em \mathrm{MeV}/{c}^2,\\ {}{\Gamma}_{\mathrm{X}(4740)}=53\pm 15\pm 11\kern0.5em \mathrm{MeV},\end{array}}$ where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the ${\mathrm{B}}_{\mathrm{s}}^0$ meson is performed and gives a value of ${m}_{{\mathrm{B}}_{\mathrm{s}}^0}=5366.98\pm 0.07\pm 0.13\kern0.5em \mathrm{MeV}/{c}^2.$

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Measurement of the CKM angle γ in B ± → DK ± and B ± → Dπ ± decays with D → $ {K}_{\mathrm{S}}^0 $h + h -

A measurement of CP -violating observables is performed using the decays B ± → DK ± and B ± → Dπ ± , where the D meson is reconstructed in one of the self-conjugate three-body final states $ {K}_{\mathrm{S}}^0 $ π + π - and $ {K}_{\mathrm{S}}^0 $ K + K - (commonly denoted $ {K}_{\mathrm{S}}^0 $ h + h - ). The decays are analysed in bins of the D -decay phase space, leading to a measurement that is independent of the modelling of the D -decay amplitude. The observables are inter- preted in terms of the CKM angle γ . Using a data sample corresponding to an integrated luminosity of 9 fb - 1 collected in proton-proton collisions at centre-of mass energies of 7, 8, and 13 TeV with the LHCb experiment, γ is measured to be $ \left({68.7}_{-5.1}^{+5.2}\right){}^{\circ} $ . The hadronic parameters $ {r}_B^{D K},{r}_B^{D\pi},{\delta}_B^{D K},\kern0.5em \mathrm{and}\kern0.5em {\delta}_B^{D\pi} $ , which are the ratios and strong-phase differences of the suppressed and favoured B ± decays, are also reported.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Producing and detecting long-lived particles at different experiments at the $\mathrn{LHC}$

We propose a new strategy to look for long-lived particles (LLP) at the LHC. The LLPs are produced at one experiment, but its decay products are detected by a detector at another experiment. We use a confining Hidden Valley scenario as a benchmark. Through showering and hadronization, the multiplicity of hidden mesons can be large, and their decay products, dimuon as chosen in this study, are typically too soft to pass triggers in traditional LHC searches. We find the best acceptance is achieved if we produce LLPs at collision points at the LHCb and ALICE experiments, and use the muon chamber of ATLAS for detection. This new search is cost-efficient since it does not require a new detector to be built. Meanwhile, it can provide coverage of interesting parameter space, which is complementary to other proposed LLP searches.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2016

Observation of the B$^{0}_{s}$ → J/ψφφ decay

The B$^{0}_{s}$ → J/ψφφ decay is observed in pp collision data corresponding to an integrated luminosity of 3 fb –1 recorded by the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV. This is the first observation of this decay channel, with a statistical significance of 15 standard deviations. The mass of the B$^{0}_{s}$ meson is measured to be 5367.08 ± 0.38 ± 0.15 MeV/c 2 . The branching fraction ratio $\mathscr{B}$(B$^{0}_{s}$ → J/ψφφ)/$\mathscr{B}$(B$^{0}_{s}$ → J/ψφ) is measured to be 0.0115 ± 0.0012 – 0.0009 + 0.0005 . In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonant B$^{0}_{s}$ → J/ψφK+K– or B$^{0}_{s}$ → J/ψK+K–K+K– decays is found.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Study of ψ(2S) production and cold nuclear matter effects in pPb collisions at $\sqrt{s_{NN}}$

The production of ψ(2S) mesons is studied in dimuon final states using proton-lead (pPb) collision data collected by the LHCb detector. The data sample corresponds to an integrated luminosity of 1.6 nb –1 . The nucleon-nucleon centre-of-mass energy of the pPb collisions is $\sqrt{s_{NN}}$ = 5 TeV. The measurement is performed using ψ(2S) mesons with transverse momentum less than 14 GeV/c and rapidity y in the ranges 1.5 < y < 4.0 and –5.0 < y < –2.5 in the nucleon-nucleon centre-of-mass system. The forward-backward production ratio and the nuclear modification factor are determined for ψ(2S) mesons. Using the production cross-section results of ψ(2S) and J/ψ mesons from b-hadron decays, the $b\bar{b}$ cross-section in pPb collisions at $\sqrt{s_{NN}}$ = 5 TeV is obtained.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Measurements of prompt charm production cross-sections in pp collisions at √s = 13 TeV

Production cross-sections of prompt charm mesons are measured with the first data from pp collisions at the LHC at a centre-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 4.98 ± 0.19 pb -1 collected by the LHCb experiment. The production cross-sections of D0, D+, Ds+, and D*+mesons are measured in bins of charm meson transverse momentum, pT, and rapidity, y, and cover the range 0 < pT< 15GeV/c and 2.0 < y < 4.5. The inclusive cross-sections for the four mesons, including charge conjugation, within the range of 1 < pT< 8 GeV/c are found to be (Formula presented.) where the uncertainties are due to statistical and systematic uncertainties, respectively.

Aaij, R↗